Dredge cutter head with counterbalancing vibrating system

ABSTRACT

A cutter dredger with a rotary cutter adjacent the mouth of a suction pipe, in which a second vibratory system balances the first vibratory system comprised by the rotating cutter and its shaft when they encounter resistance during dredging. The drive is applied to the two vibratory systems at their point of interconnection, to reduce the strain on the drive train. The drive may be mechanical, intermediate the length of a torsion shaft, or hydraulic. If hydraulic, a common pump drives motors individual to the two vibratory systems and accumulators are disposed between each pair of the pump and motors. In a compact hydraulic embodiment, the drive and the two driven systems are concentrically interconnected.

United States Patent ['19] van Heijst 451 Jan.23,1973

[75] liiv entorz vvllieiif fin "van" fieiisF D elft,

Netherlands binatie, Holland 211 App1.No.: 93,011

[30] Foreign Application Priority Data Nov. 28, 1969 Netherlands ..6917936 References Cited UNITED STATES PATENTS 12/1960 Ellicott, Jr ..37/67 8/1923 Regenbogen et a1. ..74/574 X n mun-nun-Inn Assignee: N. V. 'iaaatiaeiafaahmzrfii 3,263,450 8/1966 Condon ..64/26 2,955,472 10/1960 Krupick et a1. ....74/574 UX 703,817 7/1902 Perry ..37/66 X 2,632,318 3/1953 Meyer ..64/27 C FOREIGN PATENTS OR APPLICATIONS 473,767 3/1929 Germany 37/ 66 1,120,s3s 7/1968 Great Britain...; ..37l67 Primary Examiner-William B. Penn Assistant Examiner-Clifford D. Crowder Att0mey--Young & Thompson [57] ABSTRACT A cutter dredger with a rotary cutter adjacent the mouth of a suction pipe, in which a second vibratory system balances the first vibratory system comprised by the rotating cutter and its shaft when they encounter resistance during dredging. The drive is applied to the two vibratory systems at their point of interconnection, to reduce the strain on the drive train. The drive may be mechanical, intermediate the length of a torsion shaft, or hydraulic. 1f hydraulic, a common pump drives motors individual to the two vibratory systems and accumulators are disposed between each pair of the pump and motors. in a compact hydraulic embodiment, the drive and the two driven systems are concentrically interconnected.

6 Claims, 4 Drawing Figures PATENTEDJAN 23 I975 SHEET 1 BF 2 INVENTOR PATENTEUJMI 23 1975 SHEET 2 0F 2 IN VENTOR W/LLEM /AW VAN 65/087 ATTORNEYS DREDGE CUTTER HEAD WITH COUNTERBALANCING The present invention relates to cutter dredgers of the type in which a rotary cutting device, mounted on the end of a rotary drive shaft, is disposed adjacent the mouth of a suction pipe. During operation of such a device, vibrations will be induced in the bottom of the body of water in which the dredging takes place, and the cutting device will correspondingly vibrate either at the same frequency or at a harmonic of that frequency.

The disadvantage of devices of this type is that a very strong torque may be produced in the shaft and in the drive means for the shaft, which may overload the drive means; and this is particularly true when the cutting device encounters resistance during the dredging operation.

Accordingly, it is an object of the present invention to provide a cutter dredger in which the strain on the drive means is kept to a minimum.

Another object of the present invention is the provision of a cutter dredger having means for reducing maximum load on the drive means and adapted optionally for mechanical or hydraulic drive.

Finally, it is an object of the present invention to provide a cutter dredger which will be relatively simple and inexpensive to manufacture, easy to operate, maintain and repair, and rugged and durable in use.

Briefly, these objects are achieved, according to the present invention, by providing a second vibrating system that counterbalances the vibrating system comprised by the cutter, such that the product of the mass and frequency of vibration of the two vibrating systems is substantially equal, the two systems being interconnected and the drive means acting at the point of interconnection of the two systems.

Stated another way, two similarly tuned vibrating systems are simultaneously driven at a nodal point by the drive means, which accordingly need exert only a reduced drive effort and correspondingly receives a reduced load, particularly when an obstacle is encountered by the dredger. When an obstacle is thus encountered, the cutter is retarded so that the second or duplicating system leads, and the result is that both vibrating systems start vibrating in opposed phase. What would otherwise be the strain on the drive means is obviated by the fact that the drive means is connected at or adjacent the nodal point.

The present invention may be mechanically operated or hydraulically operated. If mechanically operated, a twistable shaft may interconnect the two vibrating systems with the drive applied to the shaft intermediate the loads. If hydraulically operated, the cutting device is connected to a hydraulic motor and the second system or counterbalancing mass is connected to a second motor, the two motors being driven by a common pump in a closed hydraulic circuit, with accumulators between the pump and each motor and also between the two motors.

An advantage of the hydraulic system is that the second vibrating system may have a higher frequency than the cutter, so that its mass may be proportionally smaller.

In a preferred embodiment, the drive and the cutter and the second system or counterbalancing mass may be related to each other as concentric sleeves carrying radially outwardly and/or inwardly directed ribs that oppose each other peripherally to define hydraulically and/or mechanically pressurized chambers between the ribs. For example, in such a concentric system, the cutter may be connected to the innermost member, the drive to the next outer member, and the second or counterbalancing vibrating system may comprise the outermost member. The interfingering ribs of the concentric members may be urged apart by fluid pressure, e.g., hydraulically, or by mechanical pressure, as by rubber members or springs.

When a hydraulic drive is used, the system may be 1 tuned by adjustment of the pressure in the accumulators.

Other objects, features and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompanying drawing, in which:

FIG. I is a somewhat schematic view of mechanically driven apparatus according to the present invention;

FIG. 2 is a schematic view but showing a second embodiment of the invention in which the drive is hydraulic;

FIG. 3 is a view of a third embodiment in which the drive and driven members are concentric; and

FIG. 4 is a side view of the general lay out of a cutter dredger.

Referring now to the drawing in greater detail, and first with reference to the embodiment of FIG. 1, there is shown a cutting dredger according to the present invention having a cutting device 1 on one end of a twistable rotary shaft 2 the other end of which carries a flywheel 3. A drive train 4 driven by a motor 5 rotates the shaft 2 and simultaneously the cutting device 1 and flywheel 3.

In operation, the cutting device 1 and flywheel 3 are driven in the same direction at the same rotary velocity and may be said to be rotating in phase with each other. When the cutting device encounters resistance during the dredging operation, however, then the shaft 2 will twist and the cutting device 1 and flywheel 3 will shift out of phase to each other, with the flywheel 3 leading. The cutting device and the flywheel mass will then vibrate in opposed phases, whereupon the shaft 2 has a torsional node at the point of application of drive train 4. Accordingly, the increased torque of portions of the system will not apply itself to the drive train 4.

FIG. 2 differs from FIG. 1 in that it discloses a hydraulic circuit 6 having a displacement pump 7 and two hydraulic displacement motors 8 and 9. Cutting device 10 is driven by motor 8, while flywheel 11 is driven by motor 9. Accumulator 12 is disposed between pump 7 and motor 8, and accumulator 13 is disposed between pump 7 and motor 9. Accumulator 14 is disposed between the motors 8 and 9 on the side of the circuit opposite pump 7. The accumulators are of the oleopneumatic type and are tunable by adjustment of the pressure of the gas therein.

In the system shown in FIG. 2, when the cutting device 10 encounters an obstacle and is retarded, there is a resulting pressure rise in associated accumulator 12. However, pump 7 then has a lower output and motor 9 then begins to lead, that is, temporarily functions as a pump. The pressure in accumulator 13 is thereupon increased. In practice, the pressure in accumulators 12 and 13 tends to rise and fall practically simultaneously.

With the pressure on opposite sides of pump 7 thus tending to remain uniform, virtually no strain is imposed on pump 7 by the fact that the cutting device 10 has encountered an obstacle. The substantially simultaneous variations in the quantity of oil in accumulators 12 and 13 are made up from accumulator 14.

An advantageous device for embodying the present invention in a simple form is shown in FIG. 3, in which the shaft of the cutting device or of a member connected thereto is shown at 15 and has radially outwardly extending ribs 16 thereon. A concentric ring 17 with inwardly extending ribs 18 and outwardly extending ribs 19 thereon surrounds shaft 15 and in turn is surrounded by ring 20 with radially inwardly extending ribs 21 thereon. The ribs 21 and 19 interfinger with wide clearance, as do the ribs 16 and 18, the latter defining chambers 22 and 23 therebetween and the former defining chambers 24 and 25 therebetween. In a mechanical embodiment, these chambers may be provided with resilient means such as rubber members or springs. In a hydraulic embodiment, the ring 17 functions like the pump 7 in FIG. 2 while the member 15 functions like the motor 8, and the ring 20 functions like the motor 9 and flywheel 11. The chambers 22-25 are connected to accumulators and the ribs that define these chambers form fluidtight partitions.

If a cutting device as in FIG. 3 encounters resistance, the member 15 is retarded and the pressure in chamber 23 and the accumulator connected thereto will rise, while the pressure in chamber 22 will fall, assuming that the members rotate clockwise. Chambers 22 and 23 have individual accumulators, as do the chambers 24 and 25; and the operation is accordingly analogous to that of FIG. 2.

In the embodiment of FIG. 3, the ring 20 of course is free to vibrate with a higher angular speed than the shaft 15 and hence may be of a mass correspondingly reduced relative to the mass of the cutter.

In view of the foregoing disclosure, therefore, it will be evident that all of the initially recited objects of the present invention have been achieved. 4

Although the present invention has been described and illustrated in connection with preferred embodi- 1 ments, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Such modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

FIG. 4 shows a ship 25, a suction tube 26, a cutter 27, a drive shaft 28 and an electro-motor 29.

What is claimed is:

1. In a cutter dredger having a suction pipe and a rotating cutter adjacent the mouth of the pipe, the cutter being connected to a shaft having drive means for rotating the shaft, whereby the cutter and shaft together constitute a first vibrating system set into vibration during dredging; the improvement comprising a second vibrating system, means interconnecting said first and second vibrating systems, said first and second vibrating systems being tuned to each other to vibrate relative to each other in opposed phase with a point of vibration reversal on said interconnecting means, said drive means driving said first and second vibrating systems simultaneously from said point of vibration reversal.

2. Apparatus as claimed in claim 1, said shaft being a twistable shaft extending on opposite sides of said drive means.

3. Apparatus as claimed in claim 2, said suction pipe inclining downwardly from said dredger to said cutter, said twistable shaft extending lengthwise of said suction pipe, said second vibrating system being disposed adjacent the upper end of the suction pipe.

4. Apparatus as claimed in claim 1, said drive means comprising a hydraulic pump, a first hydraulic displacement motor driven by said pump to rotate said cutter, a second hydraulic displacement motor driven by said pump to rotate a mass in said second vibrating system, said pump and first and second motors being interconnected by a closed hydraulic circuit, and accumulators in said circuit between said pump and said first motor, between said pump and said second motor, and between said motors.

5. Apparatus as claimed in claim 1, said shaft and drive means and second vibrating system being interconnected by concentric members having interfingering ribs thereon that define chambers between said ribs, and yieldable means between the ribs urging the ribs apart.

6. Apparatus as claimed in claim 5, said yieldable means comprising hydraulic means including fluid pressure accumulators.

* l II 

1. In a cutter dredger having a suction pipe and a rotating cutter adjacent the mouth of the pipe, the cutter being connected to a shaft having drive means for rotating the shaft, whereby the cutter and shaft together constitute a first vibrating system set into vibration during dredging; the improvement comprising a second vibrating system, means interconnecting said first and second vibrating systems, said first and second vibrating systems being tuned to each other to vibrate relative to each other in opposed phase with a point of vibration reversal on said interconnecting means, said drive means driving said first and second vibrating systems simultaneously from said point of vibration reversal.
 2. Apparatus as claimed in claim 1, said shaft being a twistable shaft extending on opposite sides of said drive means.
 3. Apparatus as claimed in claim 2, said suction pipe inclining downwardly from said dredger to said cutter, said twistable shaft extending lengthwise of said suction pipe, said second vibrating system being disposed adjacent the upper end of the suction pipe.
 4. Apparatus as claimed in claim 1, said drive means comprising a hydraulic pump, a first hydraulic displacement motor driven by said pump to rotate said cutter, a second hydraulic displacemEnt motor driven by said pump to rotate a mass in said second vibrating system, said pump and first and second motors being interconnected by a closed hydraulic circuit, and accumulators in said circuit between said pump and said first motor, between said pump and said second motor, and between said motors.
 5. Apparatus as claimed in claim 1, said shaft and drive means and second vibrating system being interconnected by concentric members having interfingering ribs thereon that define chambers between said ribs, and yieldable means between the ribs urging the ribs apart.
 6. Apparatus as claimed in claim 5, said yieldable means comprising hydraulic means including fluid pressure accumulators. 